This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
The inventors have developed several geometries to provide support of parabolic mirrors—for the sake of explanation, these are called “Series Three” and “Series Five” (with the Series Three 60 having three main triangles as viewed from the end and Series Five 62 having five main triangles as viewed from the end.) See FIGS. 16A and 16B.
Reducing frame weight will generally lead to more cost effective frames. Increasing frame rigidity (reducing deflections) will improve slope error and lead to a frame which converts a higher % of the solar energy hitting the mirrors into usable heat content/improved efficiency of the entire solar field which improves the return on investment for the solar field.
The prior WES patent applications and figures are similar to FIGS. 16A and 16B (showing Series 3 and Series 5). The Series 5 design shown in FIG. 16A is an alternate “geometry”. Since that time, further development has focused on more of a traditional space frame design where all of the struts come in to a common “unified hub” 64 (in FIG. 65, one can see how every other “hub” uses different struts). With the WES Strut End Piece and Sleeve designs, the member (struts)/forces can be brought together into very small physical spaces. Bringing all of the forces into a unified hub 64 reduces essentially any bending moments, improving the efficiency of the space frame in terms of load carrying capacity and deflection. When the WES Series 5 62 was redesigned to use a unified hub 64 configuration, there were improvements in both deflection and individual member loads, as the bending moments were relatively low due to short strut lengths and short connections between the sleeves along the chord.
FIG. 17 depicts named components of the prior patent application Series 5 multifinned sleeve and strut end piece design—useful to refer to re: nomenclature of the rest of this patent application. Note that this figure also shows the multiple parallel fins 70 of the sleeve 68, which receives a main support member 66, and/or strut end piece (redesigned as non-parallel “guided insertion” in subsequent designs). Depending on load characteristics and fasteners, the number of fins on the sleeve 68 or strut end piece can be modified; for example, below there is discussed the single fin sleeve, with one or more fins on the mating strut end piece. In the earlier WES patent applications and frame design, single finned strut end pieces were shown inserted into a dual fin sleeve arrangement.
The parabolic mirror framework supports the weight of itself and the supported mirrors and the wind and associated torque forces from the wind, which can be substantially higher than the simple weight of the assembled structure. These structures are generally 8, 12 (or other) meters long, supported at each end (or otherwise, as disclosed in the WES Rolling rib patent application) in a manner which allows rotation of the entire frame so that the parabolic mirrors follow the sun and focus the solar radiation optimally. The truss geometry and components are designed for each specific application (e.g. 8, 12 or other span lengths, wind conditions at installation location, drive mechanism and whether it acts on the solar frames individually or drives one frame rotation which in turn drives others (for 2, 3, 4, 5 or more in series, increasing/multiplying the total torque on the driven frame by the number of frames that each drive actuates)).
The forces acting on the frame are transmitted through the truss struts to the truss sleeves (nodes) which form the vertices of the triangles made up by the struts. The load capability and efficiency of the truss geometry and the capabilities of the components (struts, strut end pieces (where used), sleeves, fasteners, etc.) define how efficiently the truss performs and how optically accurate the collection of solar radiation is (leading to greater energy efficiencies).
FIG. 27A shows an angled strut end piece connecting to a “sleeve” (shown as a tubular shape, but can be a different cross section). The strut end piece transfers the tensile or compressive loads from the strut which slips over and is fastened to the strut end piece which then fastens to the sleeve (node), where various struts and/or strut end pieces concentrate their loads.
FIG. 27B shows multiple struts and strut end pieces converging their forces onto the sleeve 68 (through which passes the chord, chord couplers, segmented chords, chord connector(s), etc. defining the 8, 12 (or other) length of the solar frame). The system of struts 32, strut end pieces 30 (where used), sleeves 68 and chords are designed such that at each vertices of the frame the forces converge on a common point 76 (which may or may not be where there is actual physical material from the frame materials). This convergence to a common point 76 prevents odd bending moments at the sleeve connection.